Intraobserver and interobserver reproducibility in the evaluation of ultrasonic pachymetry measurements of central corneal thickness

Purpose: To assess reproducibility of central corneal thickness (CCT) measurement by means of ultrasonic pachymetry. Methods: Fifty one volunteers underwent three sessions of CCT measurements, each consisting of three CCT measurements, performed by each of three different observers. Intraand interobserver reproducibility was calculated by means of intraclass correlation coefficient (ICC). The expected range of variability between two independent evaluations was calculated using scatter plots of each test-retest difference against their mean. The standard deviation of the mean differences in the test-retest scores was used to describe the differences in the score spread. Results: The ICC ranges of the intra-and interobserver evaluations were 0.95 - 0.97 and 0.89 - 0.95 respectively; the expected variability was less than or equal to +/-1% and less than or equal to +/- 2% respectively (95% confidence interval). Conclusions: The measurement of CCT by means of ultrasonic pachymetry is highly reproducible.